Three of those hurt in the incident in on Friday night in Collioure were taken to hospital after the device "exploded very low" and rained down sparks on some of the 80,000 crowd, firefighters and the local prefecture said.
One person remained in hospital after surgery for a shoulder fracture.
Celebratory fire claims a life, leaves 33 others injured
The misfiring rocket was part of a show on a barge just off the port of Collioure, a small picturesque seaside town near the Spanish border whose 3,000 population mushrooms around 30-fold with summer tourists.
Three doctors on-site swiftly intervened to treat those injured, the local prefecture said, adding local police have opened an investigation into the incident.
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